The fuel cell has a construction in which an anode and a cathode are arranged with an electrostatic membrane being held therebetween. Hydrogen (fuel gas) is supplied to the anode, and oxygen (oxidizing gas) is supplied to the cathode, by which an electrochemical reaction takes place between the electrodes to generate an electromotive force.
For the fuel gas, high-pressure hydrogen (for example, 70 MPa) stored, for example, in a high-pressure hydrogen tank is supplied to the anode through a gas supply path after having been decompressed. Hydrogen discharged from the anode is sent again to the gas supply path by a fuel pump. On the other hand, for the oxidizing gas, air taken in from the outside is supplied to the cathode, for example, by using a compressor.
The fuel cell system is provided with, in addition to the aforementioned fuel pump and compressor, a large number of rotary components such as a cooling water pump for cooling the fuel cell by circulating cooling water. For these rotary components, the operation rotational speed of each of the components is set considering a power consumption, service life, noise of simple component, and the like. However, if the frequencies of noises produced from the rotary components approach each other, interference occurs when the operation rotational speed fluctuates, which poses a problem in that harsh “whining sounds” are produced.
To solve this problem, a method has been proposed in which the frequencies of noises produced during idling of the rotary components are set so as to separate 30 Hertz or more from each other (refer to Patent Document 1). According to this method, the noises produced from two or more rotary components can be prevented from being recognized as one sound, and also the whining sounds can be suppressed, so that hearing organs of human being do not feel discomfort.    Patent Document 1: JP-A-2004-178847    Patent Document 2: JP-A-H7-192743    Patent Document 3: JP-A-2005-83202